In a series of prior applications assigned to the assignee of this application, a system for vehicle brake testing has been disclosed, which incorporates an automatically controlled actuator for applying force to a vehicle brake system being tested, combined with means for measuring by dynamometer the vehicle stopping force, or brake effort, at the vehicle wheels resulting from the brake application force. One major purpose is to test for brake imbalance at the left and right wheels under various types of brake application procedures, such as rapid or slow, short period or longer period, brake pedal actuations. An important aspect of this general brake testing system is its universality of application to various vehicles, preferably in a convenient manner which permits relatively rapid transfer from one vehicle to the next in a vehicle brake testing station.
The series of related prior applications includes: SER. NO. TITLE INVENTOR(S) __________________________________________________________________________ 382,385 BRAKE PEDAL ACTUATOR William Clayton Sr. now Pat. No. and Edwin Lee Cline 3,877,299 382,538 RECORDER AND COMPUTER TYPE BRAKE Edwin Lee Cline now Pat. No. ANALYZER AND METHOD 3,899,916 563,329 BRAKE TESTING APPARATUS AND METHOD Carl Jr. Asmus and INCORPORATING HYDRAULIC POSITION- Woodrow C. Wickersham SENSITIVE SUBSYSTEM 567,286 ACTUATOR UNIT FOR VEHICLE TESTING Carl Jr. Asmus and Woodrow C. Wickersham __________________________________________________________________________
Experience with the brake testing system disclosed in the listed applications has indicated a need for a rate control system which will control the rate at which actuating force is increased during application of the vehicle braking system during a test, in response to signals indicating the brake effort as measured at one or more of the vehicle wheels during the test. A suitable rate control system will meet several needs:
1. Since no two vehicles have braking systems which perform exactly alike, and they in fact tend to have widely different performance characteristics, a rate control system permits a more uniform brake application testing cycle from vehicle to vehicle.
2. Controlling the rate of brake application makes it possible to prevent "overshoot" in the test application which would make the measured results less reliable.
3. Controlling the rate of brake effort increase permits reaching a desired brake effort level in a predetermined period of time, thereby conserving total testing time while avoiding too rapid an application.
4. A major advantage of reaching the desired brake effort level in a predetermined period of time is avoidance of excessive heat build-up (or heat soak) at the brake friction surfaces prior to the test result measurements.